cc-mode: add ‘c-lineup-ternary-bodies’ (bug#41061)

Introduce ‘c-lineup-ternary-bodies’ function which, when used as
a c lineup function, aligns question mark and colon of a ternary
operator.  For example:

    return arg % 2 == 0 ? arg / 2
                        : (3 * arg + 1);

* lisp/progmodes/cc-align.el (c-lineup-ternary-bodies): New function.
* doc/misc/cc-mode.texi (Operator Line-Up Functions): Document the
new function.
* test/lisp/progmodes/cc-mode-tests.el (c-lineup-ternary-bodies): New
test case.

1 files changed, 20 insertions, 0 deletions

diff --git a/doc/misc/cc-mode.texi b/doc/misc/cc-mode.texi
index f9c9f5e1830..16eac4828c7 100644
--- a/doc/misc/cc-mode.texi
+++ b/doc/misc/cc-mode.texi
@@ -6395,6 +6395,26 @@ function is the same as specifying a list @code{(c-lineup-assignments
 
 @comment ------------------------------------------------------------
 
+@defun c-lineup-ternary-bodies
+@findex lineup-ternary-bodies @r{(c-)}
+Line up true and false branches of a ternary operator
+(i.e. @code{?:}).  More precisely, if the line starts with a colon
+which is a part of a said operator it with corresponding question
+mark.  For example:
+
+@example
+@group
+return arg % 2 == 0 ? arg / 2
+                    : (3 * arg + 1);    @hereFn{c-lineup-ternary-bodies}
+@end group
+@end example
+
+@workswith @code{arglist-cont}, @code{arglist-cont-nonempty} and
+@code{statement-cont}.
+@end defun
+
+@comment ------------------------------------------------------------
+
 @defun c-lineup-cascaded-calls
 @findex lineup-cascaded-calls @r{(c-)}
 Line up ``cascaded calls'' under each other.  If the line begins with